1. Field of Invention
This invention relates to the field of wind turbines and more specifically to a system for illuminating wind turbines with selectively perceptible light.
2. Description of Related Art
Wind turbines in the United States kill hundreds of thousands of bats every year, an estimate far exceeding known fatalities from other human causes. Bats are important components of most ecosystems. In addition, insect eating bats save United States farmers billions of dollars each year in pest control. Bat populations are slow to recover from declines and the multiple populations adversely affected by wind turbines include endangered species such as the Hawaiian hoary bat and Indiana bat.
Concerns about the impact of turbines on bats have curtailed wind energy projects. For example, some wind turbine facility operators in the continental United States and Hawaii were required to reduce operations after their turbines killed endangered bats.
Researchers have attempted to use several methods to reduce bat fatalities, with limited success. One method restricts the operation of turbines at low wind speeds. However, this is unpredictable and results in loss of revenue and turbine efficiency without completely eliminating bat fatalities. Sound-producing devices intended to scare bats away have not proven effective. Moreover, these devices are unlikely to work at long distances because of physical limitations of sound transmission through air.
The untested method of shining bright light onto bats to produce an avoidance response would not work in the absence of precise animal targeting and identification or continuous light emission. Bright lights and loud sounds also affect habitats around the turbines and could be a nuisance. Devices that alter the operation of a turbine or activate a deterrent after detecting animals are expensive and do not effectively discriminate between animals. Some devices that effectively deter bats may cause harm to other animals, such as protected migrating birds.
There is an unmet need in the art for a practical, visually unobtrusive, and passive way to prevent bats from approaching and fatally colliding with wind turbines.